1. Field of the Invention
The present invention relates to the compression of digital video information and, more particularly, to a method and device for providing different coding strategies to obtain efficiency during decoding.
2. Description of the Related Art
Single-layer video coding is most widely used in a variety of applications, such as digital-video recording and digital television. The video is encoded at a certain bit rate, then a decoder decodes the bit-stream and outputs every picture at the encoded full quality. To reduce the computation load the reduced-complexity decoding of single-layer bit-streams has been deployed. However, as pictures are decoded at partial quality, the reference pictures used for motion compensation on the decoder side frequently do not match the ones used during encoding. As a result, errors that occur in the reference pictures propagate to other pictures. This is also known as prediction drift or error propagation.
Layered-video coding or bit-rate scalable method is an alternative to the single-layer video coding. The video is encoded first at a low bit rate to generate the base layer. The difference between the original and the base-layer-reconstructed video is then encoded to generate one or more enhancement layers. On the decoder side, the base layer is always decoded, but the enhancement layer is fully or partially decoded depending on the available processing capacity. If only the base layer is decoded, there is no prediction drift as low-quality reference pictures are used for encoding. If both the full enhancement layer and the base layer are decoded, each layer uses its corresponding reference pictures during encoding for decoding purposes, thus there is no prediction drift. However, if the enhancement layer is only partially decoded and there is a motion prediction among enhancement-layer pictures, the prediction drift occurs in the enhancement layer. Moreover, this type of coding is inherently less efficient during compression as the reference pictures used in the enhancement layer do not lend themselves to efficient motion prediction. Furthermore, the extra overhead in multi-layered coding is more complex than decoding a single-layer bit stream to produce the same quality. Accordingly, there is a need for obtaining optimal decoding performance that is relatively simple to facilitate practical implementation.